Presented by:
TAUSIF RAZA KHAN

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ABSTRACT
DISH TO DIGITAL: AMAZING GROWTH IN THE RADAR ANTENNA TECHNOLOGY
Radar is a vulnerable technology. Today’s military radar systems perform a variety of tasks which were not possible by the radar systems developed more than 6 decades ago during world war 2nd . There has been continuous efforts towards upgrading the radar system and associated technologies with drastic improvement in the performance. Almost every current radar innovation owes its existence to the advances made in the antenna technology to achieve a very high efficiency and ultra low sides lobes with computer intensive design. There has been a phenomenal growth in military radar antenna technology over the last few decades. The present paper deals with the design and development of various types of antenna systems for different military radar applications and growth in the technology over the last few decades in the country, particularly, at LRDE, a radar laboratory of Defence Research and Development Organization.
INTRODUCTION
Today’s military radar systems perform a variety of tasks that were not possible by the radar systems developed during world war 2nd . There have been continuous efforts towards upgrading the radar systems and associated technologies with drastic improvement in the performance. Almost every current radar innovation owes its existence in the advances made in the antenna technology to achieve a very high efficiency and ultra low sides lobes with computer intensive design. In recent years, the antenna and radar systems have seen amazing advancements that led the capabilities not possible few years back.
Over the last few decades, electronics and radar development establishment (LRDE) has been concentrating in developing variety of antenna systems and associated technologies for various radars developed for military use in India. LRDE has been implementing futuristic technologies in all the antenna systems and adopted various state of the art technologies to perfect the design, manufacturing and integration with radar systems successfully. To meet the radar systems requirement in terms of range, coverage and resolutions, antenna needs to generate beams shape, beam width, side lobe level and directivity with the additional ability to steer the beam is formed and how the beam is steered.
Antenna technology has gone through several changes commensurate with the evolution of complex radar systems for various military applications. Present radar gives an overview of the antenna system and related technologies developed over the years to meet the requirement of armed forces. For the sake of convenience, the development of antenna systems has been categorized in terms of how the antenna beam of the required beam width, side lobe level, gain and other antenna characteristics are steered to give the volumetric coverage of the entire space the radar is looking intro.
ANTENNAS AND ANTENNA ARRAYS :-
An antenna is defined by Webster’s Dictionary as ‘’usually metallic device(as a rod or wire) for radiating or receiving radio waves “. The IEEE standard defination of terms for antennas defines the antenna or aerial as a “means for radiating or receiving radio waves “. In other words the antenna is the transitional structure between free space and a guiding device. The guiding device or transmission line may take the form of a coaxial line or waveguide, and it is used to transport the electromagnetic energy from the transmitting source to the antenna or from the antenna to the receiver.
There are various types of antennas such as wire antennas(dipoles, loop, helix etc ) aperture antenna(waveguide, horn, reflectors), array antenna, lens antenna etc. Antenna is characterized by various parameters, the most important ones are the gain (directivity) and the radiation pattern of the antenna.
To enhance the directivity of the antenna and to have the desired radiation pattern, number of antennas are grouped to form an array. An antenna array is an assembly of antennas in an electrical and geometrical configuration where elements are identical in most of the cases. Based on the elements used, these would include slotted arrays, microstrip array, or dipole array. The array can be classified as linear array, curvillinear array, planar array, and conformal array.
REQUIREMENTS OF RADAR ANTENNAS :-
The radar antenna is a distinctive and important part of any radar. It serves the following functions :
1) Act as the transducer between propagation in space and guided wave propagation in the transmission lines.
2) Concentrates the radiated energy in the direction of the target .
3) Collects the echo energy scattered back to the radar from a target.
4) Measures the angle of arrival of the received echo signal so as to provide the location of the target in azimuth, elevation or both.
5) Acts as a spatial filter to separate targets in the angle domain and rejects undesired signals from directions other than the main beam.
6) Provides the desired volumetric coverage of the radar.
7) Usually establishes the time between radar observations of a target.